Mutually insulated bridging contacts for heavy currents

ABSTRACT

A multiple bridging contact for each conduction path of a contactor has a common support member and two adjacent bridging contact elements mounted therein. Each bridging contact element has at each end a contact plate for cooperation with stationary contact plates of the contactor. An insulating wall is disposed within the support member between the adjacent bridging contact elements for preventing conduction from one bridging contact element to the other.

finite States Patent Quario Sept. 26, 1972 MUTUALLY INSULATED BRIDGING 3,272,949 7 9/1966 Lawrence ..200/ 166 D CONTACTS FOR HEAVY CURRENTS 1,795,641 3/1931 Dante ..200/ 144 R tor: Gian Quafi), Torino Russell X [73] Assignee: Ghisalba S.p.A., Torino, Italy Primary ExaminerI-l. 0. Jones 22 FiledZ Dec. 0,1970 Attorney-Young & Thompson [21] pp 96,737 [57 ABSTRACT A multiple bridging contact for each conduction path Foreign ApPllcatlon Iy Data of a contactor has a common support member and Jan. 9, 1970 Italy ..67058 A/70 two adjacent bridging Contact elements mounted therein. Each bridging contact element has at each 52 us. 01. ..200/l66D end a Contact Plate cooperatibn with Stationary 51 1111.0. .110111 1/34 Contact plates of the contactor" An insulating Wall is [58] Field of Search, 2()()/166 L, 166 BC, 151 149 disposed within the support member between the ad- A, ZOO/143R, 144 R, 16 A, 166 BR, 1665 I jacent bridging contact elements for preventing conduction from one bridging contact element to the [56] References Cited Other- UNITED STATES PATENTS 4 Claims, 4 Drawing Figures 3,200,225 8/1965 Lemke "200/166 D 'IIIIIII" PATENTEDSEPZB I912 3.694.605

INVENTOR G/AN AU/G/ Game ATTORNEYS MUTUALLY INSULATED BRIDGING CONTACTS FOR HEAVY CURRENTS BACKGROUND OF THE INVENTION This invention relates to a multiple contact bridge for double break contactors, particularly for heavy current electromagnetic contactors.

It is well known that the movable contacts of the contactors intended for heavy currents may be advantageously subdivided into two or more part contacts each independently pushed against a common stationary contact, thus obtaining overall a more extensive contact surface and reducing energy loss, heat production and, indirectly, wear of contacts. This is therefore usually done in simple break contactors.

On the contrary it has not hitherto been possible to apply a similar feature in double break contactors for heavy currents, wherein each movable contact is in the form of a contact bridge having at both ends contact plates for co-operating with the corresponding stationary contact plates connected to the wire conductors between which the contactor is provided for making and breaking electrical connection. In such double break contactors, breaking takes place at two spaced points for each conduction path. If two or more bridging contact elements are mounted directly side by side in a common support member for each conduction path of such a contactor, reciprocal welding of two adjacent bridging contact elements is to be expected sooner or later, thus preventing their independent movement and removing the advantages of the feature.

In effect, the two contact plates of each bridging contact element open in a succession whose sequence is casual, and therefore it sometimes occurs that the first opened contact plate of a first bridging contact element, and the first opened contact plate of a second bridging contact element, adjacent to the first one, are situated at opposite ends of the contact bridge. In such a case the current passes for a short time from a first stationary contact to the first bridging contact element through the not yet opened contact plate, then from the first bridging contact element to the second adjacent one through the reciprocally contacting side surfaces of both bridging contact elements, and finally from said second bridging contact element to the second stationary contact through the second not yet opened contact plate. As the mutually contacting side surfaces of both bridging contact elements have only an uncertain conductivity, at some point on said surfaces an arc will form and, if the break has taken place under heavy current, both bridging contact elements locally melt and weld together. For avoiding such an event the two bridging contact elements should be mounted in separate support members, that is practically, the conduction paths of the contactor should be doubled, and the consequent burden in design, size and costs cannot be accepted.

BRIEF SUMMARY OF THE INVENTION The object of this invention is to allow use of multiple contact bridges, i.e., of contact bridges comprising each two or more bridging contact elements, even in double break contactors for heavy currents, and this by using simple technical means without increasing noticeably the complexity and the cost of the contactor.

0 through the common metallic support member of the bridging contact elements may remain, but it has been found that such a conduction cannot give rise to damage due to the low conductivity of said support member in comparison with the bridging contact elements. In effect said support member has no conduction purpose but only mechanical tasks, and it is usually made of steel or stainless steel.

This invention will appear more clearly from the following description, drawn up with reference to a non limiting example of embodiment, diagrammatically shown in the annexed drawing.

BRIEF DESCRIPTION OF THE DRAWINGS In the annexed drawing:

FIG. 1 shows, as viewed in the direction of the contact plates, a multiple contact bridge according to the invention, comprising a pair of bridging contact elements mounted in a common support member;

FIG. 2 is a view perpendicular to that of FIG. 1, wherein in the left hand portion the corresponding stationary contact is also shown, while the right hand portion is sectional along the line IIII of FIG. 1;

FIG. 3 is an end view of FIG. 2 in the direction of arrow F3;

FIG. 4-shows a section, taken along the line IVIV of FIG. 2, of the rest means for the compression springs of the contacts, and of the insulating wall which is connected to said rest means.

DETAILED DESCRIPTION The double break movable contact as shown has a per se known, U-shaped support member 1 connected to a driving stirrup 2 of the contactor, shown by dot and dash lines in FIG. 2. Through the support member 1 pass cross pins 3 for retaining in its place a profiled metallic plate 4 intended for backing to the compression' springs 5 which provide for the correct pressure of the movable contact plates, to be described later, against the facing stationary contacts 6, 7, when the contactor is in its closed configuration.

According to the invention, within the support member 1 two or more bridging contact elements, respectively 8, 9 are side by side mounted, and each bridging contact element has at its ends two contact plates, respectively 10, ll, 12 and 13.

The compression springs 5 of the bridging contact elements, which on the one hand act against the bridging contact elements 8, 9 in the vicinity of their ends, rest on the other hand against insulating blocks 14, 15 fixedly mounted at the ends of the profiled plate 4 Between the adjacent bridging contact elements 8, 9 (or between each pair of adjacent bridging contact elements when these are more than two) there is an insulating wall 16. The vicinity of the contact plates 10 to 13 the insulating wall 16 ends are somewhat retracted so as not to touch the stationary contacts when the contactor is closed, while on the otherhand the insulating wall .16 preferably reachesto the insulating blocks l4, 15 to which it may be connected.-ln-the illustrated embodiment, said insulating wall 16 has a central extension 17 which protrudes through a corresponding opening of the profiled plate 4. To said extension 17 are connected by a rivet 18 two side cheeks 19 which cannot pass through the opening in the profiled plate 4 and thus retain in place the insulating wall 16.

Said insulating wall 16 prevents electrical contact between the facing surfaces of both bridging contact elements 8, 9 and thus the described event of the reciprocal welding between the bridging contact elements cannot take place. In this manner the bridging contact elements remain surely independent from one another in their movements.

As already stated, when the contact plates and 13, or 11 and 12, mounted on the opposite ends of the separate bridging contact elements 8 and 9, remain for a short time close to the stationary contacts 6 and 7 during break, a current conduction between both bridging contact elements 8 and 9 is still possible through the common support member 1 which embraces both bridging contact elements by touching their outer side surfaces. When'needed, such conduction may be avoided by placing insulating plates similar to the insulating plate 16, between the outer side surfacesof the bridging contact elements, and the inner side surfaces of the support member 1. it has been found, however, that in view of the different kind of metals forming the bridging contact elements (usually made of silver plated copper) and the support member (usually made of stainless steel), and also in view of the relatively high electrical resistance of the support member, such a conduction involves a very low current, it cannot give rise to damage and therefore there is no need for taking precautions against it. Oh the contrary, the springs 5 may be damaged by any current passing therethrough, and for this reason they are protected against conduction by resting upon the blocks 14, made of electrically insulating material, instead of resting directly against the profiled plate 4 as usual.

As already stated, the bridging contact elements for each conduction path of the contactor, mounted in a common support member, may also be more than two, and in such cases an insulating wall 16 is needed between each bridging contact element and each other adjacent bridging contact element. Thus, two insulating walls are needed when three bridging contact elements are present, or three insulating walls when four bridging contacts are provided for, and so on.

Therefore, the invention makes it possible to use tactor intended for a lighter current will receive in said su ort members, as usual, single contact brid cs.

avmg thus described my invention, what I c aim is:

l. A multiple contact bridge for each conduction path of a double breakcontactor, comprising a common support member, at least two bridging contact elements mounted side by side within said common support member, at least one insulating wall mounted within said common support member between each bridging contact element and each other bridging contact element adjacent thereto, a profiled metal plate, cross pins in said common support member for retaining said profiled metal plate, and compression springs between said profiled metal plate and each bridging contact element. 4

2. A multiple contact bridge as set forth in claim 1, and blocks of an electrically insulating material fixedly mounted at both ends of said profiled plate, said compression springs acting between said insulating blocks and each bridging contact element.

3. A multiple contact bridge as set forth in claim 1, and an opening in said profiled metal plate, said insulating wall having an extension passing through said, opening in said profiled metal plate and protruding therefrom, and retaining means mounted in the protruding extension of said insulating wall.

4. A multiple contact bridge for each conduction way of a double break contactor, comprising a common support member, two bridging contact elements mounted side by side within said common support member, a profiled metal plate, cross pins in said common support member for retaining said profiled metal plate, blocks of an electrically insulating material fixedly mounted at both ends of said profiled metal plate, compression springs acting between said insulating blocks and each bridging contact element, an insulating wall mounted withinsaid common support member between said two bridging contact elements, said profiled metal plate having an aperture therein, and said insulating wall having an extension passing through said aperture in said profiled metal plate, and retaining means mounted in the extension of said insulating wall. 

1. A multiple contact bridge for each conduction path of a double break contactor, comprising a common support member, at least two bridging contact elements mounted side by side within said common support member, at least one insulating wall mounted within said common support member between each bridging contact element and each other bridging contact element adjacent thereto, a profiled metal plate, cross pins in said common support member for retaining said profiled metal plate, and compression springs between said profiled metal plate and each bridging contact element.
 2. A multiple contact bridge as set forth in claim 1, and blocks of an electrically insulating material fixedly mounted at both ends of said profiled plate, said compression springs acting between said insulating blocks and each bridging contact element.
 3. A multiple contact bridge as set forth in claim 1, and an opening in said profiled metal plate, said insulating wall having an extension passing through said opening in said profiled metal plate and protruding therefrom, and retaining means mounted in the protruding extension of said insulating wall.
 4. A multiple contact bridge for each conduction way of a doublE break contactor, comprising a common support member, two bridging contact elements mounted side by side within said common support member, a profiled metal plate, cross pins in said common support member for retaining said profiled metal plate, blocks of an electrically insulating material fixedly mounted at both ends of said profiled metal plate, compression springs acting between said insulating blocks and each bridging contact element, an insulating wall mounted within said common support member between said two bridging contact elements, said profiled metal plate having an aperture therein, and said insulating wall having an extension passing through said aperture in said profiled metal plate, and retaining means mounted in the extension of said insulating wall. 